How much to charge for planning a pastry menu?

Hey all! Odd first post, but my wife is a pastry chef (a WOOOONDERFUL one!) and recently got a gig designing the pastry section of a restaurant's menu. She is working for a friend who is designing the bulk of the menu and asked her to do the pastries, but this is a first for her and she isn't quite sure how much a job like this typically gets paid.